The Hordaland Womens's Cohort. A longitudinal study on urinary incontinence in middle-aged women

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Abstract

Urinary incontinence (UI) is a prevalent problem among middle-aged women, and
many epidemiological studies have investigated this problem. Most of these studies
are cross-sectional and only few longitudinal studies have been conducted. Thus, the
knowledge about incidence, remission and natural history of UI is scarce. The aim of
that present dissertation was to answer major epidemiological questions about
incidence, progress and remission of UI in middle-aged women.

The Hordaland Women’s Cohort was established in 1997 and designed as a
prospective longitudinal study for 15 years. The source population was from
Hordaland Health Study (HUSK), which was a joint epidemiological research project
and a part of national health project called Cohort of Norway (CONOR). HUSK
invited all individuals in Hordaland County born between 1953-57, and among 14300
women in Hordaland, almost 9900 (70%) participated in HUSK. We took a one-fifth
random sample of female HUSK participants and 2230 women consented to take part
in the Women’s Cohort. In 2007 the Cohort reached a ten-year follow up with six
checkpoints and the present dissertation is based on the analyses of data for this
period of the Cohort.

In the first sub-study (Paper I), the data from source (HUSK) population was used to
compare the basic demographic data and urologic characteristics between the women
who participated in the Cohort and rest of the women in HUSK. For demographic
data, 2230 women in the Cohort were compared with 7746 women in HUSK, who
were not selected for the Cohort. For urologic characteristics, we used a HUSK subquestionnaire
with 5320 participants. Of these, 1920 were in the Cohort and we compared their urological characteristics with those of the rest of the women
(n=3400). The results demographic data showed a very high similarity for
demographic data. The only significant differences were observed for higher
education (p=0.001) and higher annual family income (p=0.018) among the women
in the Cohort.

Analyzing data for urinary conditions showed few statistical differences between
women in the Cohort and the rest of the women; they had somewhat more UI
(p=0.040), more stress UI (p=0.048) and less amount of leakage (p=0.015) in the
Cohort participants. Prevalence rate of any UI was 28.9% in the Cohort and 24.8% in
the rest of women in HUSK. This paper also described the research methodology in
details with intention of using it as reference for any further data analysis from the
Cohort.

The second sub-study (Paper II) explored the prevalence, incidence and remission of
UI. In this paper the possibility of an early prevalence peak in middle-aged women
was investigated. We first used all data from the Cohort, which was gathered during
ten years in six waves, to analyze the prevalence curve of UI. Furthermore, for more
detailed analyses of prevalence, incidence and remission, data from the women who
answered all six questionnaires were used. We sorted data in terms of age with eight
groups in the age span of 41-55 years. Definition of UI was based on the results from
the Incontinence Severity Index (ISI) and women with an ISI of more than 0 were
defined as having incontinence. Women with an ISI equal to 3 or more, who reported
their UI to be bothersome, were defined as having significant UI. According to our
data, the prevalence of any UI in women aged 41-42 year was about 37% and
increased gradually up to 50% in the age of 51-52 years, after which it started to
decrease gradually. The changing patterns for incidence and remission were the same
until age 51-52, but then the incidence started to decrease while the remission was
increasing, which could have caused the peak in the prevalence of UI. Stress UI was
the major type and most cases of UI were of low severity. Over the observation
period, while the proportion of mixed UI increased by age, the proportion of stress UI
remained relatively stable and the proportion of urgency UI slightly varied between aged groups. Regarding type shift, proportion of moderate UI remained relatively
stable, while slight UI decreased and severe/very severe UI increased by age.

The main aim of the third sub-study (Paper III) was to investigate the natural history
of UI with focus on finding the new-onset UI and its changes in types and severity.
First we defined continent women in the baseline by using the same definition of UI
as in Paper II. We followed them wave by wave during 10 years and 5 checkpoints.
Almost half of them reported to have UI, at least once during 10 years. The types of
new-onset UI by type were distributed as: 49.8% stress, 18.3% urgency and 20.3%
mixed UI. By severity, 89.3% of women started with slight UI, none of them reported
severe UI in the first report. In follow up of women for 2 waves after the new-onset
UI, one-third of them had persistent UI, the type and severity was mainly stress UI
with slight severity, with a low tendency for shifting the type or severity. We also
suggest out that mixed UI is not necessarily the final stage of UI.

Paper II: Jahanlu D, Hunskaar S. The Hordaland Women's Cohort: prevalence, incidence, and remission of urinary incontinence in middle-aged women. Int Urogynecol J 2010;21:1223-9. The article is not available in BORA due to publisher restrictions. The published version is available at: http://dx.doi.org/10.1007/s00192-010-1172-7

Paper III: Jahanlu D, Hunskaar S. Type and severity of new-onset urinary incontinence in middle-aged women: The Hordaland women's cohort. Neurourol Urodyn 2010;30:87-92. The article is not available in BORA due to publisher restrictions. The published version is available at: http://dx.doi.org/10.1002/nau.20966